As scaling continues to ever smaller feature sizes, integrated circuit (IC) reliability is an increasing concern in IC fabrication technology. The impact of trace interconnect failure mechanisms on device performance and reliability demand much more from integration schemes, interconnect materials, and processes. An optimal low-k dielectric material and its related deposition, pattern lithography, etching and cleaning are required to form dual-damascene interconnect patterns. A hard-mask scheme approach of interconnects-patterning wafer fabrication is the ability to transfer patterns into under layers with tightest optimal dimension control.
As technology nodes advance to nanotechnology, metal hard-mask materials such as TiN are used to gain better etching/removal selectivity, better pattern retention and profile control to the low-k materials during the pattern etching process.
Compositions have been developed to pullback or remove these types of metal hard-masks from substrates. The following patents are representative.
US 2006/0226122 discloses a wet etching composition including hydrogen peroxide; an organic onium hydroxide; and an acid. In another embodiment, the invention relates to a method of wet etching metal nitride selectively to surrounding structures comprising one or more of silicon, silicon oxides, glass, PSG, BPSG, BSG, silicon oxynitride, silicon nitride and silicon oxycarbide and combinations and mixtures thereof and/or photoresist materials, including steps of providing a wet etching composition including hydrogen peroxide, an organic onium hydroxide, and an organic acid; and exposing a metal nitride to be etched with the wet etching composition for a time and at a temperature effective to etch the metal nitride selectively to the surrounding structures.
US 2011/0147341 discloses an etching solution for titanium-based metals, tungsten-based metals, titanium/tungsten-based metals or their nitrides. The etching solution contains 10-40 mass % hydrogen peroxide, 0.1-15 mass % of an organic acid salt, and water.
U.S. Pat. No. 7,922,824 discloses an oxidizing aqueous cleaning composition and process for cleaning post-plasma etch residue and/or hardmask material from a microelectronic device having said residue thereon. The oxidizing aqueous cleaning composition includes at least one oxidizing agent, at least one oxidizing agent stabilizer comprising an amine species selected from the group consisting of primary amines, secondary amines, tertiary amines and amine-N-oxides, optionally at least one co-solvent, optionally at least one metal-chelating agent, optionally at least one buffering species, and water. The composition achieves highly efficacious cleaning of the residue material from the microelectronic device while simultaneously not damaging the interlevel dielectric and metal interconnect material also present thereon.
U.S. Pat. No. 7,928,046 discloses an aqueous, silicate free, cleaning compositions of about pH 9 or below and method of using the cleaning compositions for cleaning microelectronic substrates, which compositions are able to essentially completely clean such substrates and produce essentially no metal corrosion of the metal elements of such substrates. The aqueous cleaning compositions of present invention have (a) water, (b) at least one of ammonium and quaternary ammonium ions and (c) at least one of hypophosphite (H2PO2−) and/or phosphite (HPO32−) ions. The cleaning compositions also may contain fluoride ions. Optionally, the composition may contain other components such as organic solvents, oxidizing agent, surfactants, corrosion inhibitors and metal complexing agents.
US 2013/0045908 discloses a semiconductor processing composition and method for removing photoresist, polymeric materials, etching residues and copper oxide from a substrate comprising copper, low-k dielectric material and TiN, TiNxOy or W wherein the composition includes water, a Cu corrosion inhibitor, at least one halide anion selected from Cl− or Br−, and, where the metal hard mask comprises TiN or TiNxOy, at least one hydroxide source.
WO 2013/101907 A1 discloses compositions comprising etchants including hexafluorosilicic acid and hexafluorotitanate, at least one oxidant including high valent metals, peroxide or high oxidation state species and at least one solvent.
US 2013/0157472 discloses a semiconductor processing composition and method for removing photoresist, polymeric materials, etching residues and copper oxide from a substrate comprising copper, low-k dielectric material and TiN, TiNxOy or W wherein the composition includes water, at least one halide anion selected from Cl− or Br−, and, where the metal hard mask comprises only TiN or TiNxOy, optionally at least one hydroxide source.
US 2012/0058644 A1 (BASF) discloses a liquid composition free from N-alkylpyrrolidones and hydroxyl amine and its derivatives, having a dynamic shear viscosity at 50° C. of from 1 to 10 mPas as measured by rotational viscometry and comprising based on the complete weight of the composition, (A) of from 40 to 99.95% by weight of a polar organic solvent exhibiting in the presence of dissolved tetramethylammonium hydroxide (B) a constant removal rate at 50° C. for a 30 nm thick polymeric barrier anti-reflective layer containing deep UV absorbing chromophoric groups, (B) of from 0.05 to <0.5% of a quaternary anunonium hydroxide, and (C)<5% by weight of water; method for its preparation, a method for manufacturing electrical devices and its use for removing negative-tone and positive-tone photoresists and post etch residues in the manufacture of DD Stacked Integrated Circuits and 3D Wafer Level Packagings by way of patterning Through Silicon Vias and/or by plating and bumping.
US 2009/0131295 A1 discloses compositions for removing and cleaning resist, etching residues, planarization residues, metal fluorides and/or metal oxides from a substrate are provided, the composition including a metal ion-free fluoride compound and water. The resist, etching residues, planarization residues, metal fluorides and/or metal oxides are generated during one or more patterning processes during which a metal hard mask is used.
Compositions based on peroxides for TiN removal have been described in the prior art. These have incorporated alcohol amine bases in aqueous solvent systems and solvent-rich systems. A key problem of previous compositions has been the instability of the compositions once peroxide is added. This appears to be due to the use of oxidizable components in the composition which lead to the decomposition of hydrogen peroxide in the composition and its de-activation. This inherent instability has necessitated expensive point of use mixing of the peroxide with the remaining components of the composition and has limited the ability to use the prior art chemistries in a recycle-mode.
In addition to its use as hard mask material, TiN is also often used as a metallic adhesion or liner layer for metal plugs at the MO level. While PVD TiN is used for forming a hard mask over large regions of the wafer prior to plasma etching, PVD deposition methodology does not readily provide the kind of conformal deposition required for depositing the liner prior to deposition of the high aspect ratio metal plugs. Chemical Vapor Deposition (CVD) is ideally suited to deposit such conformal coatings, and is typically used for forming the TiN adhesion layer. Ideally a wet chemistry designed for removing the TiN hard mask after the plasma etching process, should not etch the TiN liner. Depending on the type of metal plug, this can pose a difficult challenge, because the hardmask and adhesion layer TiN are often very similar in chemical composition.
Compositions of the prior art show no selectivity for etching of PVD TiN used in a hard mask vs. etching of CVD TiN used in a metal liner or adhesion layer. In those compositions high TiN hard mask removal will also likely coincide with some liner/adhesion layer loss. Accordingly, there is a need in the art for a stripper composition that does not suffer from the above-mentioned drawbacks.